I. Field of Use
The present application relates to the field of home security. More specifically, the present application relates to a particular type of door or window sensor for use in home security applications.
II. Description of the Related Art
Security systems for homes and offices have been around for many years. Often, these systems make use of barrier alarms, such as door and window sensors, in communication with a centrally-located alarm panel. Door and window sensors typically comprise two distinct parts: a magnet and a reed switch assembly. The magnet is typically installed onto a movable part of a window or onto a door edge, while the reed switch is mounted to a stationary surface, such as a wall adjacent to a door or window frame. When the door or window is closed, the magnet and reed switch are in close proximity to one another, and a relatively strong magnetic field is sensed by the reed switch, causing the switch to maintain a first state indicative of a “no alarm” condition. If the door or window is opened, proximity is lost between the magnet and the reed switch, resulting in a loss of the magnetic field in proximity to the reed switch, thus causing the reed switch to change state, e.g., from closed to open or from open to closed. The change of state is indicative of a local alarm condition (i.e., unauthorized opening of a door or window), and a signal may be generated by circuitry located within the reed switch assembly and sent, via wires or over-the-air, to the alarm panel. Alternatively, or in addition, a loud audible alert is generated, either at the alarm panel in the home or directly by the circuitry within the reed switch assembly, indicating that a door or window has been opened without authorization.
One of the disadvantages of typical door and window sensors is that they are only able to operate in a “binary” fashion: the reed switch is either open or closed. Thus, prior art sensors are not capable of determining how far a door or window has been opened.
Another disadvantage of prior art door and window sensors is that they may be defeated by placing an external magnet in proximity to the reed switch, thus allowing a door or window to be opened without causing an alarm.
Yet another disadvantage of prior art door and window sensors is that they must typically be mounted so that they are in very close proximity to the magnet when a door or window is closed. This is sometimes problematic when wide door or window frames, casements, casings, or jambs are encountered. The relatively wide displacement between the sensor and magnet in these situations does not allow the reed switch to change state when a door or window is closed.
Thus, it would be desirable to overcome the shortcomings of the prior art to provide door and window sensors that can be used on wide door/window frames, jambs, casements, or casings.